Oilfield apparatus and methods of use

ABSTRACT

The invention in one of its aspects provides a connection apparatus for a subsea hydraulic circuit and method of use in a sampling application. The apparatus comprises a longitudinal body configured to be removably docked with a subsea hydraulic circuit receptacle. The body comprises a plurality of radial ports axially displaced along the body, and an axial bore accommodating a spool having at least one fluid barrie. The spool and fluid barrier are actuable to be axially moved in the bore to control axial flow paths along the bore between the plurality of radial ports. The apparatus may be configured as a sampling hot stab in an application to sampling a production fluid from a subsea hydrocarbon production system.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.14/396,660, filed Oct. 23, 2014, which is a U.S. National Stage Entry ofInternational Patent Application No. PCT/GB2013/051059, filed Apr. 26,2013, which claims the benefit of U.S. Provisional Patent ApplicationNo. 61/639,020, filed Apr. 26, 2012, the disclosures of which are herebyincorporated entirely herein by reference.

BACKGROUND

Technical Field

The present invention relates to oilfield apparatus and methods of use,and in particular to a sampling apparatus (such as a sampling chamber, asampling test circuit, sampling tools), and methods of use for fluidintervention and sampling in oil and gas production or injectionsystems. The invention has particular application to subsea oil and gasoperations, and aspects of the invention relate specifically to methodsand apparatus for combined fluid injection and sampling applications.

State of the Art

In the field of oil and gas exploration and production, it is common toinstall an assembly of valves, spools and fittings on a wellhead for thecontrol of fluid flow into or out of the well. Such flow systemstypically include a Christmas tree, which is a type of fluid manifoldused in the oil and gas industry in surface well and subsea wellconfigurations. A Christmas tree has a wide range of functions,including chemical injection, well intervention, pressure relief andwell monitoring. Christmas trees are also used to control the injectionof water or other fluids into a wellbore to control production from thereservoir.

There are a number of reasons why it is desirable to access a flowsystem in an oil and gas production system (generally referred to as an“intervention”). In the context of this specification, the term “fluidintervention” is used to encapsulate any method which accesses a flowline, manifold or tubing in an oil and gas production, injection ortransportation system. This includes (but is not limited to) accessing aflow system for fluid sampling, fluid diversion, fluid recovery, fluidinjection, fluid circulation, fluid measurement and/or fluid metering.This can be distinguished from full well intervention operations, whichgenerally provide full (or near full) access to the wellbore. Full wellintervention processes and applications are often technically complex,time-consuming and have a different cost profile to fluid interventionoperations. It will be apparent from the following description that thepresent invention has application to full well intervention operations.However, it is an advantage of the invention that full well interventionmay be avoided, and therefore preferred embodiments of the inventionprovide methods and apparatus for fluid intervention which do notrequire full well intervention processes.

International patent application numbers WO00/70185, WO2005/047646 andWO2005/083228 describe a number of configurations for accessing ahydrocarbon well via a choke body on a Christmas tree. Although a chokebody provides a convenient access point in some applications, themethods of WO00/70185, WO2005/047646, and WO2005/083228 do have a numberof disadvantages. Firstly, a Christmas tree is a complex andcarefully—designed piece of equipment. The choke performs an importantfunction in production or injection processes, and its location on theChristmas tree is selected to be optimal for its intended operation.Where the choke is removed from the choke body, as proposed in the priorart, the choke must be repositioned elsewhere in the flow system tomaintain its functionality. This compromises the original design of theChristmas tree, as it requires the choke to be located in a sub-optimalposition.

Secondly, a choke body on a Christmas tree is typically not designed tosupport dynamic and/or static loads imparted by intervention equipmentand processes. Typical loads on a choke body in normal use would be ofthe order of 0.5 to 1 tonnes, and the Christmas tree is engineered withthis in mind. In comparison, a typical flow metering system ascontemplated in the prior art may have a weight of the order of 2 to 3tonnes, and the dynamic loads may be more than three times that value.Mounting a metering system (or other fluid intervention equipment) onthe choke body therefore exposes that part of the Christmas tree toloads in excess of those that it is designed to withstand, creating arisk of damage to the structure. This problem may be exacerbated indeepwater applications, where even greater loads may be experienced dueto thicker and/or stiffer components used in the subsea infrastructure.

In addition to the load restrictions identified above, positioning theflow intervention equipment on the choke body may limit the accessavailable to large items of process equipment and/or access of divers orremotely operated vehicles (ROVs) to the process equipment or otherparts of the tree.

Furthermore, modifying the Christmas tree so that the chokes are innon-standard positions is generally undesirable. It is preferable fordivers and/or ROV operators to be completely familiar with theconfiguration of components on the Christmas tree, and deviations in thelocation of critical components are preferably avoided.

Another drawback of the prior art proposals is that not all Christmastrees have chokes integrated with the system; approaches which rely onChristmas tree choke body access to the flow system are not applicableto these types of tree.

It is amongst the objects of the invention to provide a method andapparatus for accessing a flow system in an oil and gas productionsystem, which addresses one or more drawbacks or disadvantages of theprior art. In particular, it is amongst the objects of the invention toprovide a method and apparatus for fluid intervention in an oil and gasproduction system, which addresses one or more drawbacks of the priorart. An object of the invention is to provide a flexible method andapparatus suitable for use with and/or retrofitting to industry standardor proprietary oil and gas production manifolds, including Christmastrees.

It is an aim of at least one aspect or embodiment of the invention toprovide an apparatus which may be configured for use in both a subseafluid injection operation and a production fluid sampling operation anda method of use.

An aim of at least one aspect of the invention is to provide an improvedsampling apparatus for oil and gas operations and methods of use. Otheraims and objects of the invention include providing an improved samplingchamber, a sampling test circuit, sampling tools, and/or methods forfluid intervention which are improved with respect to sampling apparatusand method of the prior art. A further aim of at least one aspect of theinvention is to provide a sampling apparatus and method of use whichfacilitates the use of novel flow system access methods and fluidintervention operations.

Further objects and aims of the invention will become apparent from thefollowing description.

SUMMARY

According to a first aspect of the invention there is provided asampling apparatus for a hydrocarbon production system, the samplingapparatus comprising:

-   -   a sampling chamber;    -   a fluid inlet and a fluid outlet to the sampling chamber, the        fluid inlet and fluid outlet configured to be in communication        with a production fluid flowing in a production flow bore; and    -   a sampling port in fluid communication with the sampling        chamber;    -   wherein the sampling apparatus comprises a formation configured        to be exposed to a production fluid flowing in the production        bore and create a pressure differential between the fluid inlet        and fluid outlet which drives production fluid from the        production bore into the sampling chamber via the fluid inlet.

Preferably the formation is configured to create a Venturi effect whichreduces the pressure in the production bore in an area closer to thefluid outlet than the fluid inlet. The formation may reduce the pressurein the production bore adjacent or substantially adjacent the fluidoutlet.

The formation may comprise a flow restriction in the production bore.The flow restriction may be arranged such that the narrowest point ofthe production bore (at least in a locality of the sampling apparatus)is adjacent or substantially adjacent to the fluid outlet.

Preferably the apparatus is configured to circulate fluid through thesampling chamber via the fluid inlet and fluid outlet.

An opening to the fluid inlet may at least partially be oriented to facea prevailing flow direction of production fluid in the production bore.This may assist in directing flow into the fluid inlet. An opening tothe fluid outlet may at least partially be oriented perpendicular to aprevailing flow direction of production fluid in the production bore.This may assist in exposing the fluid outlet to an area of reduced localpressure, and enhance circulation of fluid through the samplingapparatus.

The sampling chamber may be disposed radially of the production bore,and may be located in a side bore formed to the production bore.

At least a part of the sampling chamber may be located above theproduction bore, and in one embodiment, the sampling chamber is locatedentirely above the production bore. In this configuration, theproduction fluid is drawn into the sampling chamber against the effectof gravity.

At least a part of the sampling chamber may be located below theproduction bore, and in one embodiment, the sampling chamber is locatedentirely below the production bore. In this configuration, theproduction fluid is drawn into the sampling chamber with assistance fromthe effect of gravity.

The sampling chamber may comprise one or more baffles. The sampling portmay comprise a stem which extends into the sampling chamber. An openingto the stem may be located in a lower portion of the sampling chamber.Thus the opening to the stem may be configured to preferentiallywithdraw liquid phase fluids from the sampling chamber.

The formation may be disposed asymmetrically in the production flow bore(i.e. on one side of the production bore).

The hydrocarbon production system may be a subsea hydrocarbonproduction, and the production flow bore may be a subsea flow line froma subsea well operating in production mode.

The sampling apparatus may be configured to collect a sample of aproduction fluid flowing in a production flow bore via the fluid inletwhen in a sampling mode; and may be configured to provide an injectionflow path for an injection fluid from an injection fluid conduit to theproduction flow bore when operating in an injection mode.

According to a second aspect of the invention there is provided ahydrocarbon production system comprising:

-   -   a production flow bore;    -   a sampling apparatus associated with the production flow bore,        the sampling apparatus having a sampling chamber, a fluid inlet        and a fluid outlet to the sampling chamber in communication with        a production fluid flowing in a production flow bore; and a        sampling port in fluid communication with the sampling chamber;    -   wherein the production flow bore comprises a formation which        when exposed to a production fluid flowing in the production        bore which creates a pressure differential between the fluid        inlet and fluid outlet which drives production fluid from the        production bore into the sampling chamber via the fluid inlet.

The sampling apparatus may have a first mode of operation in which asample of a production fluid flowing in a production flow bore iscollected via the fluid inlet; and may have a second mode of operationin which the sampling apparatus provides an injection flow path for aninjection fluid from an injection fluid conduit to the production flowbore.

Embodiments of the second aspect of the invention may include one ormore features of the first aspect of the invention or its embodiments,or vice versa.

According to a third aspect of the invention there is provided a methodof collecting a sample of fluid from a hydrocarbon production system,the method comprising: providing a sampling apparatus associated with aproduction flow bore, the sampling apparatus having a sampling chamber,a fluid inlet and a fluid outlet to the sampling chamber incommunication with a production fluid flowing in a production flow bore;and a sampling port in fluid communication with the sampling chamber;

-   -   exposing the flow of production fluid to a formation to create a        pressure differential between the fluid inlet and fluid outlet        which drives production fluid from the production bore into the        sampling chamber via the fluid inlet.

The method may comprise, in an injection mode of operation, passing aninjection fluid from an injection fluid conduit through a flow path inthe sampling apparatus to the production flow bore. The method maycomprise, in a sampling mode of operation, collecting a sample of aproduction fluid flowing in a production flow bore via the fluid inlet.

Embodiments of the third aspect of the invention may include one or morefeatures of the first or second aspects of the invention or theirembodiments, or vice versa.

According to a fourth aspect of the invention there is provided asampling apparatus for a hydrocarbon production system, the samplingapparatus comprising:

-   -   a sampling chamber;    -   a fluid inlet and a fluid outlet to the sampling chamber, the        fluid inlet and fluid outlet configured to be in communication        with a production fluid flowing in a production flow bore;    -   wherein the sampling apparatus is configured to collecting a        sample of a production fluid flowing in a production flow bore        via the fluid inlet when in a sampling mode; and is configured        to provides an injection flow path for an injection fluid from        an injection fluid conduit to the production flow bore when        operating in an injection mode.

The flow path may pass through the sampling chamber or a part thereof.The sampling apparatus may be configured to be disposed in an injectionbore of the hydrocarbon production system. Preferably the flow path isan alternate flow path to those of the sampling conduits, including thepaths created fluid inlet, fluid outlet and/or the sampling port (i.e.it is not necessary for the injection fluid to pass through the fluidinlet, fluid outlet or sampling ports.

The sampling apparatus may comprise a formation configured to be exposedto a production fluid flowing in the production bore and create apressure differential between the fluid inlet and fluid outlet whichdrives production fluid from the production bore into the samplingchamber via the fluid inlet.

Embodiments of the fourth aspect of the invention may include one ormore features of the first to third aspects of the invention or theirembodiments, or vice versa.

According to a fifth aspect of the invention there is provided ahydrocarbon production system comprising:

-   -   a production flow bore;    -   a sampling apparatus associated with the production flow bore,        the sampling apparatus having a sampling chamber for collecting        a sample of a production fluid flowing in a production flow        bore;    -   wherein the sampling apparatus has a first mode of operation in        which a sample of a production fluid flowing in a production        flow bore is collected via the fluid inlet;    -   and wherein the sampling apparatus has a second mode of        operation in which the sampling apparatus provides an injection        flow path for an injection fluid from an injection fluid conduit        to the production flow bore.

The production flow bore may comprise a formation which when exposed toa production fluid flowing in the production bore which creates apressure differential between the fluid inlet and fluid outlet whichdrives production fluid from the production bore into the samplingchamber via the fluid inlet.

The sampling apparatus may comprise ports which define an injection flowpath through the sampling apparatus in an injection mode.

The sampling apparatus may be configured to have a first condition insampling mode. The injection flow path may be closed in the firstcondition. The sampling apparatus may be configured to have a secondcondition in an injection mode, in which the injection flow path isopen.

The sampling apparatus may be configured to be moved from a firstcondition to a second condition by injection fluid pressure.

The hydrocarbon production system may comprise an isolation valveoperatively associated with the sampling apparatus. In the firstcondition, the isolation valve may be closed and may isolate thesampling chamber from injection fluid.

Embodiments of the fifth aspect of the invention may include one or morefeatures of the first to fourth aspects of the invention or theirembodiments, or vice versa.

According to a sixth aspect of the invention there is provided a methodof collecting a sample of fluid from a hydrocarbon production system,the method comprising:

-   -   providing a sampling apparatus associated with a production flow        bore, the sampling apparatus having a sampling chamber, a fluid        inlet and a fluid outlet to the sampling chamber in        communication with a production fluid flowing in a production        flow bore;    -   in an injection mode of operation, passing an injection fluid        from an injection fluid conduit through a flow path in the        sampling apparatus to the production flow bore.

The method may comprise, in a sampling mode of operation, collecting asample of a production fluid flowing in a production flow bore via thefluid inlet.

The method may comprise exposing the flow of production fluid to aformation to create a pressure differential between the fluid inlet andfluid outlet which drives production fluid from the production bore intothe sampling chamber via the fluid inlet.

Embodiments of the sixth aspect of the invention may include one or morefeatures of the first to fifth aspects of the invention or theirembodiments, or vice versa.

According to a seventh aspect of the invention there is provided amethod of injecting an injection fluid into a hydrocarbon productionsystem using the apparatus or systems of any previous aspect of theinvention.

Embodiments of the seventh aspect of the invention may include one ormore features of the first to sixth aspects of the invention or theirembodiments, or vice versa.

According to an eighth aspect of the invention there is provided aconnection apparatus for a subsea hydraulic circuit, the connectionapparatus comprising: a longitudinal body configured to be removablydocked with a subsea hydraulic circuit receptacle, the longitudinal bodycomprising a plurality of radial ports axially displaced along the body;

-   -   wherein the body comprises an axial bore accommodating a spool        having at least one fluid barrier;    -   and wherein the spool and fluid barrier are actuable to be        axially moved in the bore to control axial flow paths along the        bore between the plurality of radial ports.

The connection apparatus is preferably a hot stab hydraulic connectioninterface, configured to be received in a standard hot stab receptacle.

The fluid barrier may be an annular fluid barrier to seal an annulusbetween the spool and the bore. The apparatus may comprise at leastthree radial ports, and the spool and fluid barrier may be actuable tobe axially moved from a first position in which a flow path between afirst port and a second port is open, and a second position in which aflow path between the second port and a third port is open. In the firstposition a flow path from the third port to the first or second ports ispreferably closed. In the second position, a flow path from the firstport to the second or third ports is preferably closed.

Embodiments of the eighth aspect of the invention may include one ormore features of the first to seventh aspects of the invention or theirembodiments, or vice versa.

According to a ninth aspect of the invention there is provided a hotstab apparatus for a remotely operated vehicle, the hot stab apparatuscomprising:

-   -   a longitudinal body configured to be removably docked with a hot        stab receptacle, the longitudinal body comprising a plurality of        radial ports axially displaced along the body;    -   wherein the body comprises an axial bore accommodating a spool        having at least one fluid barrier;    -   and wherein the spool and fluid barrier are actuable to be        axially moved in the bore to control axial flow paths along the        bore between the plurality of radial ports.

Embodiments of the ninth aspect of the invention may include one or morefeatures of the first to eighth aspects of the invention or theirembodiments, or vice versa.

The invention encapsulates methods of use of the apparatus of the eighthand ninth aspects in a hydrocarbon fluid sampling operation.

According to a tenth aspect of the invention there is provided a methodof collecting a sample of fluid from a hydrocarbon production system,comprising using the apparatus of the eighth aspect of the invention todeliver a sample of fluid from the hydrocarbon production system to asample collection vessel.

Embodiments of the tenth aspect of the invention may include one or morefeatures of the first to ninth aspects of the invention or theirembodiments, or vice versa.

According to an eleventh aspect of the invention there is provided amethod of collecting a sample of fluid from a hydrocarbon productionsystem, the method comprising: providing a sample collection vessel anda sampling hot stab apparatus in fluid communication with the samplecollection vessel;

-   -   locating the sampling hot stab apparatus in a receptacle of the        hydrocarbon production system, the receptacle being in fluid        communication with a production fluid in the hydrocarbon        production system;    -   collecting production fluid in the sample collection vessel via        the sampling hot stab apparatus;    -   flushing the sampling hot stab apparatus prior to removal of the        sampling hot stab apparatus from the receptacle.

The method may comprise providing a test hot stab apparatus, andcoupling the test hot stab apparatus to the sample collection chamberand/or hydrocarbon production system.

The method may comprise decanting a pre-charged fluid from the samplecollection vessel into the hydrocarbon production system, and maycomprise controlling the decanting of the pre-charged fluid from thesample collection vessel using the test hot stab apparatus. Decantingthe pre-charged fluid from the sample collection vessel may compriseflushing the sampling hot stab apparatus.

The method may comprise controlling the collection of production fluidinto the sample collection vessel using the test hot stab apparatus.

The method may comprise flushing the sampling hot stab apparatus using ahydraulic fluid source coupled to the test hot stab apparatus, and/ormay comprise controlling the flow of fluid through the sampling hot stabapparatus using the test hot stab apparatus.

The sampling hot stab apparatus may be a hot stab apparatus according toan embodiment of the tenth aspect of the invention, and the method maycomprise actuating movement of the spool and fluid barrier of the hotstab apparatus using the test hot stab apparatus.

Embodiments of the eleventh aspect of the invention may include one ormore features of the first to tenth aspects of the invention or theirembodiments, or vice versa.

According to a twelfth aspect of the invention there is provided asystem for collecting a sample of fluid from a hydrocarbon productionsystem, the system comprising: a subsea hydraulic circuit comprising asample collection vessel, a connection apparatus, and a receptacle for ahydraulic interface apparatus;

-   -   wherein the connection apparatus is configured to be coupled to        the production system to connect the hydraulic circuit to the        production system;    -   wherein the hydraulic circuit is configured to enable a        production fluid to be delivered to the sample collection vessel        via the connection apparatus;    -   and wherein the hydraulic circuit is configured to enable        flushing of at least the connection apparatus.

The hydraulic circuit may be configured to enable flushing of theconnection apparatus by actuation of the hydraulic interface apparatus,and/or may be configured to enable flushing of the connection apparatusfrom a hydraulic fluid source coupled to the hydraulic interfaceapparatus.

The hydraulic circuit may be configured to enable flushing of theconnection apparatus with a pre-charged fluid decanted from the samplecollection chamber.

The connection apparatus may be a connection apparatus according to thetenth aspect of the invention.

The hydraulic interface apparatus is an ROV test hot stab. In oneembodiment, the system comprises a combined fluid injection and samplingapparatus.

Embodiments of the twelfth aspect of the invention may include one ormore features of the first to eleventh aspects of the invention or theirembodiments, or vice versa.

According to a thirteenth aspect of the invention there is provided aremotely operated vehicle comprising the connection apparatus of theninth aspect of the invention.

Embodiments of the thirteenth aspect of the invention may include one ormore features of the first to twelfth aspects of the invention or theirembodiments, or vice versa.

According to a fourteenth aspect of the invention there is provided asubsea production fluid sample collection system comprising theconnection apparatus of the tenth aspect of the invention.

Embodiments of the fourteenth aspect of the invention may include one ormore features of the first to thirteenth aspects of the invention ortheir embodiments, or vice versa.

According to a fifteenth aspect of the invention there is provided acombined fluid injection and sampling apparatus for a subsea oil and gasproduction flow system, the apparatus comprising:

-   -   a body defining a conduit therethrough;    -   a first connector for connecting the body to the flow system;    -   a second connector for connecting the body to a fluid injection        apparatus;    -   wherein, in use, the conduit provides an injection path from the        intervention apparatus to the flow system;    -   and wherein the apparatus further comprises a sampling subsystem        for collecting a fluid sample from the flow system.

Preferably the sampling chamber is in fluid communication with the flowsystem via the first connector.

The apparatus preferably comprises a third connector for connecting theapparatus to a downstream flowline such as a jumper flowline. Thereforethe apparatus may be disposed between a flowline connector and a jumperflowline, and may provide a flow path from the flow system to the jumperflowline, and may also establish an access point to the flow system, viathe conduit and the first connector.

The second connector may comprise a hose connector. The apparatus maycomprise a hose connection valve, which may function to shut off and/orregulate flow from a connected hose through the apparatus. The hoseconnection valve may comprise a choke, which may be adjusted by an ROV(for example to regulate and/or shut off injection flow).

Preferably the apparatus comprises an isolation valve between the firstconnector and the second connector. The isolation valve preferably has afailsafe close condition, and may comprise a ball valve or a gate valve.The apparatus may comprise a plurality of isolation valves.

The sampling subsystem may comprise an end effector, which may beconfigured to divert flow to a sampling chamber of the samplingsubsystem of the apparatus, for example by creating a hydrodynamicpressure.

An inlet to the sampling chamber may be fluidly connected to the firstconnector. An outlet to the sampling chamber may provide a fluid pathfor circulation of fluid through the chamber and/or exit to a flowline.

Preferably, the sampling subsystem comprises a sampling port, and mayfurther comprise one or more sampling needle valves. The samplingsubsystem may be configured for use with a sampling hot stab.

The sampling subsystem may be in fluid communication with the flowsystem via a flow path extending between the first and third connectors.Alternatively or in addition the sampling subsystem may be in fluidcommunication with the flow system via a flow path extending between thefirst and third connectors.

Alternatively or in addition the sampling subsystem may be in fluidcommunication with the flow system via at least a portion of aninjection bore.

Embodiments of the fifteenth aspect of the invention may include one ormore features of the first to fourteenth aspects of the invention ortheir embodiments, or vice versa. In particular, apparatus or systems ofthe first to ninth aspects of the invention may be configured with asampling subsystem as described (to be used with in a samplingoperation) and/or an injection flow path (for use in an injectionoperation), and the apparatus or systems of the first to ninth aspectsof the invention may be configured for just one of sampling orinjection.

According to a sixteenth aspect of the invention there is provided asubsea oil and gas production system comprising:

-   -   a subsea well; a subsea Christmas tree in communication with the        well; and a combined fluid injection and sampling unit;    -   wherein the a combined fluid injection and sampling unit        comprises a first connector connected to the flow system and a        second connector for connecting the body to an intervention        apparatus;    -   wherein, in use, the conduit provides an injection path from an        injection apparatus to the flow system;    -   and wherein the apparatus further comprises a sampling subsystem        for collecting a fluid sample from the flow system.

The system may further comprise an injection hose, which may beconnected to the combined fluid injection and sampling unit. The hosemay comprise an upper hose section and a subsea hose section. The upperand subsea hose sections may be joined by a weak link connector. Theweak link connector may comprise a first condition, in which theconnection between the upper hose and the subsea hose is locked, and asecond (operable) condition, in which the upper hose is releasable fromthe subsea hose.

Embodiments of the sixteenth aspect of the invention may include one ormore features of the first to fifteenth aspects of the invention ortheir embodiments, or vice versa.

According to a seventeenth aspect of the invention there is provided amethod of performing a subsea intervention operation, the methodcomprising:

-   -   providing a subsea well and a subsea flow system in        communication with the well;    -   providing a combined fluid injection and sampling apparatus on        the subsea flow system, the combined fluid injection and        sampling apparatus comprising a first connector for connecting        the apparatus to the flow system and a second connector for        connecting the apparatus to a fluid injection apparatus;    -   connecting an injection hose to the second connector;    -   accessing the subsea flow system via an injection bore between        the first and second connectors.

Preferably the access hub is pre-installed on the subsea flow system andleft in situ at a subsea location for later performance of a subseaintervention operation. The injection hose may then be connected to thepre-installed unit and the method performed.

Preferably the method is a method of performing a fluid interventionoperation. The method may comprise fluid sampling, fluid diversion,fluid recovery, fluid injection, fluid circulation, fluid measurementand/or fluid metering.

The method may be a method of performing a well scale squeeze operation.

The method may comprise performing a well fluid sampling operation. Apreferred embodiment of the invention comprises: (a) performing a fluidinjection operation; and (b) performing a well fluid sampling operation.Preferably the fluid injection operation and the well fluid samplingoperation are both carried out by accessing the subsea flow system viathe intervention path of the access hub.

Embodiments of the seventeenth aspect of the invention may include oneor more features of the first to sixteenth aspects of the invention ortheir embodiments, or vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

There will now be described, by way of example only, various embodimentsof the invention with reference to the drawings, of which:

FIGS. 1A and 1B show schematically a subsea system in accordance with anembodiment of the invention, used in successive stages of a well squeezeoperation;

FIGS. 2A and 2B show schematically the subsea system of FIGS. 1A and 1Bused in successive stages of a production fluid sample operation;

FIG. 3 is a sectional view of a combined injection and sampling hub usedin the systems of FIGS. 1 and 2, when coupled to an injection hoseconnection;

FIG. 4 is a sectional view of a sampling chamber which may be used withthe combined injection and sampling system of FIG. 3 in an embodiment ofthe invention, shown in an injection mode;

FIG. 5 is a sectional view of the sampling chamber of FIG. 4 in asampling mode;

FIG. 6 is a sectional view of a sampling chamber according to analternative embodiment of the invention;

FIG. 7 is a sectional view of a sampling chamber according to analternative embodiment of the invention;

FIGS. 8A and 8B are sectional views of a sampling tool according to anembodiment of the invention, in closed and open positions respectively;

FIG. 9 is a schematic view of a sampling test circuit according to anembodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring firstly to FIGS. 1 to 3, a combined injection and samplingsystem will be described. The system, generally depicted at 600, isshown schematically in different stages of a subsea injection operationin a well squeeze application in FIGS. 1A and 1B and in a sampling modeas described below with reference to FIGS. 2A and 2B. A hub 650,configured as a combined sampling and injection hub used in the methodsof FIGS. 1 and 2, is shown in more detail in FIG. 3.

The system 600 comprises a subsea flow system 610 which includes subseamanifold 611. The subsea manifold 611 is a conventional vertical dualbore Christmas tree (with internal tree components omitted forsimplicity), and the system 600 utilises a hub 650 to provide access tothe flow system 610. A flowline connector 630 of a production branchoutlet conduit (not shown) is connected to the hub 650 which provides asingle access point to the system. At its opposing end, the hub 650comprises a standard flowline connector 654 for coupling to aconventional jumper 656. In FIG. 1A, the hub 650 is shown installed witha pressure cap 668. Optionally a debris and/or insulation cap (notshown) may also be provided on the pressure cap 668.

The system 600 also comprises an upper injection hose 670, deployed froma surface vessel (not shown). The upper injection hose 670 is coupled toa subsea injection hose 672 via a weak link umbilical coupling 680,which functions to protect the subsea equipment, including the subseainjection hose 672 and the equipment to which it is coupled frommovement of the vessel or retrieval of the hose. The subsea injectionhose 672 is terminated by a hose connection termination 674 which isconfigured to be coupled to the hub 650. The hub 650 is configured as acombined sampling and injection hub, and is shown in more detail in FIG.3 (in a condition connected to the hose connection 674 in the mode shownin FIG. 1B).

As shown most clearly in FIG. 3, the hose connection termination 674incorporates a hose connection valve 675, which functions to shut offand regulate injection flow. The hose connection valve 675 in thisexample is a manual choke valve, which is adjustable via an ROV toregulate injection flow from the hose 672, through the hose connection674 and into the hub 650. The hose connection 674 is connected to thehub via an ROV style clamp 677 to a hose connection coupling 688.

The hub 650 comprises an injection bore 682 which extends through thehub body 684 between an opening 686 from the main production bore 640and the hose connection coupling 688. Disposed between the opening 688and the hose connection coupling 688 is an isolation valve 690 whichfunctions to isolate the flow system from injection flow. In thisexample, a single isolation valve is provided, although alternativeembodiments may include multiple isolation valves in series. Theisolation valve 690 is a ball valve, although other valve types(including but not limited to gate valves) may be used in alternativeembodiments of the invention. The valve 690 is designed to have afail-safe closed condition (in embodiments with multiple valves at leastone should have a fail-safe closed condition).

The hub 650 is also provided with a sampling chamber 700. The samplingchamber comprises an inlet 702 fluidly connected to the injection bore682, and an outlet 704 which is in fluid communication with the mainproduction bore 640 downstream of the opening 686. The sampling chamber700 is provided with an end effector 706, which may be pushed down intothe flow in the production bore 640 to create a hydrodynamic pressurewhich diverts flow into the injection bore 682 and into the samplingchamber 700 via the inlet 702. Fluid circulates back into the mainproduction bore via the outlet 704.

In an alternative configuration the inlet 702 may be fluidly connecteddirectly to the production bore 640, and the end effector 706 may causethe flow to be diverted into the chamber 700 directly from the bore 640via the inlet.

The sampling chamber 700 also comprises a sampling port 708, whichextends via a stem 710 into the volume defined by the sampling chamber.Access to the sampling port 708 is controlled by one or more samplingneedle valves 712. The system is configured for use with a sampling hotstab 714 and receptacle which is operated by an ROV to transfer fluidfrom the sampling chamber into a production fluid sample bottle (as willbe described below with reference to FIGS. 2A and 2B).

The operation of the system 600 in an application to a well squeezeoperation will now be described, with reference to FIGS. 1A and 1B. Theoperation is conveniently performed using two independently operated ROVspreads, although it is also possible to perform the operation with asingle ROV. In the preparatory steps a first ROV (not shown) inspectsthe hub 650 with the pressure cap 668 in place, in the condition asshown in FIG. 1A. Any debris or insulation caps (not shown) are detachedfrom the hub 650 and recovered to surface by the ROV. The ROV is thenused to inspect the system for damage or leaks and to check that thesealing hot stabs are in position. The ROV is also used to check thatthe tree and/or jumper isolation valves are closed. Pressure tests areperformed on the system via the sealing hot stab (optionally a fullpressure test is performed), and the cavity is vented. The pressure cap668 is then removed to the ROV tool basket, and can be recovered tosurface for inspection and servicing if required.

The injection hose assembly 670/672 is prepared by setting the weak linkcoupling 680 to a locked position and by adjusting any trim floats usedto control its buoyancy. The hose connection valve 675 is shut off andthe hose is pressure tested before setting the hose pressure to therequired deployment value. A second ROV 685 is deployed below the vessel(not shown) and the hose is deployed overboard to the ROV. The ROV thenflies the hose connection 674 to the hub 650, and the connection 674 isclamped onto the hub and pressure tested above the isolation valve 690via an ROV hot stab. The weak link 680 is set to its unlocked positionto allow it to release the hose 670 from the subsea hose 672 and the hub650 in the event of movement of the vessel from its location orretrieval of the hose.

The tree isolation valve is opened, and the injection hose 672 ispressurised to the desired injection pressure. The hose connection valve675 is opened to the desired setting, and the isolation valve is opened.Finally the production wing isolation valve is opened to allow injectionflow from the hose 672 to the production bore to commence and thesqueeze operation to be performed. On completion, the sequence isreversed to remove the hose connection 674 and replace the pressure cap668 and any debris/insulation caps on the hub 650.

It is a feature of this aspect and embodiment of the invention that thehub 650 is a combined injection and sampling hub; i.e. the hub can beused in an injection mode (for example a well squeeze operation asdescribed above) and in a sampling mode as described below withreference to FIGS. 2A and 2B.

The sampling operation may conveniently be performed using twoindependently operated ROV spreads, although it is also possible toperform this operation with a single ROV. In the preparatory steps, afirst ROV (not shown) inspects the hub 650 with its pressure cap 668 inplace (as shown in FIG. 2A). Any debris or insulation cap fitted to thehub 650 is detached and recovered to surface by a sampling Launch andRecovery System (LARS) 720. The ROV is used to inspect the system fordamage or leaks, and to check that the sealing hot stabs are inposition.

The sampling LARS 720 subsequently used to deploy a sampling carousel730 from the vessel (not shown) to depth and a second ROV 685 flies thesampling carousel 730 to the hub location. The pressure cap 668 isconfigured as a mount for the sampling carousel 730. The samplingcarousel is located on the pressure cap locator, and the ROV 685 indexesthe carousel to access the first sampling bottle 732. The hot stab (notshown) of the sampling bottle is connected to the fluid sampling port708 to allow the sampling chamber 700 to be evacuated to the samplingbottle 732. The procedure can be repeated for multiple bottles asdesired or until the bottles are used.

On completion, the sample bottle carousel 730 is detached from thepressure cap 668 and the LARS 720 winch is used to recover the samplebottle carousel and the samples to surface. The debris/insulation cap isreplaced on the pressure cap 668, and the hub is left in the conditionshown in FIG. 2A.

The embodiment described with reference to FIG. 3 has a particularconfiguration of combined injection and sampling unit, but otherconfigurations are within the scope of the invention, including thosewith differing flow control valve and isolation valve configurations.Furthermore, while the sampling chamber 700 of the unit 650 is suitablefor many applications, it is desirable to provide a more compact unitwhich is particularly easy to deploy and install on a subsea flowsystem. FIGS. 4 and 5 are a sectional view of an improved samplingapparatus according to a preferred embodiment of the invention, in whicha sampling chamber is configured for flow-through of injection fluidswhen an injection mode.

The sampling apparatus, generally shown at 100 in a combined injectionand sampling unit 101, comprises a cylindrical body 102 which is locatedin an enlarged bore portion 104 of the injection bore 106. Thecylindrical body 102 defines a volume which is a continuation of theinjection bore, such that injection fluid flows downwards through theapparatus (and through the isolation valve 690) and into the enlargedbore portion. The cylindrical body supports a sleeve 108, which isslidable (i.e. moves axially) within the cylindrical body and enlargedbore portions. A spring 110 located between the cylindrical body and thesleeve urges the sleeve towards an upward position (shown in FIG. 5). Anannular shoulder 112 at the top end of the sleeve and an annularshoulder 114 at a lower end of the cylindrical body provide respectivelyupper and lower bearing surfaces for the spring 110. A secondaryshoulder 116 is provided on an outer surface of the sleeve 108 part wayalong its length.

The lower end of the sleeve 108 is closed (other than a sampling inlet118 and a sampling outlet 120 which will be described in more detailbelow) by a profiled end cap 122. The sleeve is provided with radialports 124, circumferentially arranged around the sleeve and locatedtowards a lower end of the sleeve. When the sleeve is in its uppercondition, as shown in FIG. 5, the radial ports 124 are retracted intothe cylindrical body 102. An elastomeric seal ring 126 provides anannular seal between the sleeve and the cylinder when the sleeve is inan upper retracted position, as shown in FIG. 5.

The sampling apparatus 100 also comprises a sampling port 128, whichextends via a stem 130 into a sampling chamber 132. Access to thesampling port 128 is controlled by one or more sampling needle valves134. The sampling apparatus is configured for use with a sampling hotstab and a receptacle which is operated by an ROV to transfer fluid fromthe sampling chamber into a production fluid sample bottle as will bedescribed below.

The embodiment described with reference to FIGS. 4 and 5 provides ahighly compact construction, with the sampling chamber 132 locatedcoaxially with an injection bore 106. This reduces the overall size andweight of the apparatus, rendering it particularly suitable for subseadeployment operations.

This embodiment offers the additional advantage that it can be operatedin an injection mode. During injection of fluids via the injection bore106, fluid passes into the enlarged bore portion 104 and into theinterior of the sleeve 108. Pressure increases on the interior of thesleeve until the force on the sleeve overcomes the biasing force due tothe spring 110. The spring is compressed and the sleeve moves downwardsuntil the secondary shoulder 116 of the sleeve engages with the lowershoulder 114 on the cylindrical body, as shown in FIG. 4. In thisposition, the radial ports 124 are open to the main production bore 105,and the injection fluid flows out of the injection bore and into theproduction bore to the reservoir. The spring force is selected such thatthe sleeve is only opened in the presence of a sufficient injectionpressure in the injection bore. When injection stops, the spring forceretracts the sleeve into the cylinder, to the position shown in FIG. 5.

In a sampling mode there is no injection flow, and the isolation valve690 is closed. The sleeve is in its upper position in the cylindricalbody, as shown in FIG. 5. The profiled end cap 122 of the sleeve 108 ispartially inserted into the main production bore 105, and is configuredto create a Venturi effect which reduces pressure in the main productbore adjacent the sampling outlet 120. A pressure differential betweenthe sampling outlet 120 and sampling inlet 118 causes fluid in the mainproduction bore to be driven into the sampling chamber via the samplinginlet. Fluid circulates back into the main production bore via thesampling outlet 120. The Venturi effect can be moderated by changing theprofile of the end cap 122 and/or the depth at which the end cap is setinto the flow. It will be appreciated that flow of fluid into thechamber may also (or alternatively) be facilitated by externallycreating a small pressure drop between the inlet and the outlet, forexample by locating a flow restriction device such as a valve or Venturiprofile in the main flow bore between the sampling inlet and samplingoutlet positions.

The circulation of fluid through the chamber 132 ensures that theselected fluids are a representative sample of the recent flowcomposition (rather than a “stale” fluid sample). This is facilitated bydesigning the chamber with appropriate positioning of internal bafflesand tube runs. In addition, the positioning of internal baffles and tuberuns is such that liquids are preferentially retained in the samplingchamber (rather than gas phase fluids). For example, the internalopening of the sampling outlet tube is located in an upper part of theinternal volume of the sampling chamber so that it tends to draw out anygas in the chamber via the sampling outlet.

When collection of a sample is required, an ROV operates the samplingneedle valve 134 to allow pressure in the sampling chamber to drive thefluid from the sampling chamber, through the sampling port, to acollection vessel via a series of valves and flow lines.

Although the embodiment described with reference to FIGS. 4 and 5 isconfigured for use in the combined injection and sampling application,its compact size and relative simplicity also renders it suitable fordedicated sampling of systems and processes (i.e. those which do notneed to allow for the passage of injection fluids). FIG. 6 is asectional view of a dedicated sampling apparatus, generally shown at200, comprises a cylindrical body 202 which is located in a side bore206 formed to a main production bore 205 in the subsea flow system, andis similar to the sampling apparatus 700 of FIG. 3. A lower end of thecylindrical body 202 is closed (other than a sampling inlet 218 and asampling outlet 220 which will be described in more detail below) by aprofiled end cap 222, which is similar in form and function to theprofiled end cap 122 of the sampling apparatus 122 of FIGS. 4 and 5. Thecylindrical body 202 is in a fixed orientation in the side bore 206. Asampling port 228 extends via a stem 230 into a sampling chamber 232defined by the cylindrical body, and access to the sampling port iscontrolled by one or more sampling needle valves 234. As before, thesampling apparatus 200 is configured for use with a sampling hot staband a receptacle which is operated by an ROV to transfer fluid from thesampling chamber into a production fluid sample bottle.

Operation of the sampling apparatus 200 is as described with referenceto the previous embodiment when in its sampling mode: the profiled endcap 222 of the apparatus 200 is partially inserted into the mainproduction bore 205, and creates a Venturi effect which reduces pressurein the main flow bore adjacent the sampling outlet 220. Fluid circulatesback into the sampling chamber via the inlet 218 and back into the mainproduction bore via the sampling outlet 220. The Venturi effect can bemoderated by changing the profile of the end cap 222 and/or the depth atwhich the end cap is set into the flow, and may be facilitated byexternally creating a small pressure drop between the inlet and theoutlet. An internal baffle 236 and tubes are positioned to obtainrepresentative samples and preferentially retain liquids in the samplingchamber (rather than gas phase fluids).

A sampling apparatus 250 according to an alternative embodiment of theinvention is shown in sectional view in FIG. 7. The Figure is alongitudinal section through a sampling side bore 256, perpendicular toan axial direction of a main production flow bore. The samplingapparatus 250 of this embodiment is gravity assisted and facilitates thecollection of liquids into the chamber. The side bore 256 extends acrossand below the axis A of the main production bore. A sampling block 258is accommodated in the side bore and defines a sampling chamber volume282 located below the main production bore. The block 258 also definesflow conduits in the apparatus. The sampling block 258 comprises anaperture 260 which is aligned with substantially coaxially with the mainproduction bore. However, the aperture 260 is profiled to create areduced diameter section in the production bore. In this example, thereduced diameter section is substantially oval, with two sideprotrusions 262 a, 262 b which impinge into the flow path whichcorresponds to the main production bore. The sampling block 258 is alsoprovided with a sampling inlet 268 and a sampling outlet 270. Thesampling inlet 268 comprises an opening 272 formed in one sideprotrusion of the block, substantially facing the direction of fluidflow in the main bore. This opening connects to a fluid conduit 274which is formed in the axial direction of the side bore and the block,to direct flow to a lower end of the block where it is in communicationwith the sampling chamber 282. The outlet 270 is provided in thesampling block between the aperture and the sampling chamber andprovides a recirculation path for the production fluid. The apparatusalso comprises a sampling port 278 which extends from the lower part ofthe sampling chamber to a sampling bottle via a system of valves andflow conduits 284.

In use, fluid flow through the main bore impinges on the sideprotrusions 262 a, 262 b created by the aperture profile of the samplingblock. A proportion of the fluid flow enters the opening to the samplinginlet 268, and is redirected down the fluid conduit 274 of the inlet toenter the sampling chamber 282. The fluid is circulated out of theoutlet 270 and back into the aperture 256 to join the main productionbore. Flow through the sampling chamber via the inlet and outlet isassisted by a Venturi effect created by the restricted flow portionwhich creates a pressure drop between the inlet and the outlet. Inaddition, flow into the inlet is assisted by gravity. This embodimenthas particular benefits in collecting liquid phase fluids which tend topass along the walls of the production bore, as opposed to gas phasefluids which preferentially travel along the centre of the bore.

It will be appreciated that in other configurations, the aperture mayhave a different shape (e.g. may be circular or asymmetrical) and maycomprise multiple openings to one or more sampling inlets.

The sampling apparatus configurations of FIGS. 4 to 7 are compact insize, low in weight, and have few (or no) moving parts. They provideflow through sampling chambers which facilitate the collection ofrepresentative samples of production fluids. The small size and weightlends the design to subsea deployment and installation, and moreoverprovide a wide range of installation options. In particular, thesampling apparatus of aspects and embodiments of the invention aresuitable for installation in locations very close to the flowline, sothat the chamber is maintained at the temperature of the flowingproduction fluid, and the sampling apparatus may be located close to amanifold such as a Christmas tree. The invention is particularlysuitable for use and/or incorporation with hubs and/or hub assemblieswhich facilitate convenient intervention operations by facilitatingaccess to the flow system in a wide range of locations. These includelocations at or on the tree, including on a tree or mandrel cap,adjacent the choke body, or immediately adjacent the tree between aflowline connector or a jumper. Alternatively the apparatus of theinvention may be used in locations disposed further away from the tree.These include (but are not limited to) downstream of a jumper flowlineor a section of a jumper flowline; a subsea collection manifold system;a subsea Pipe Line End Manifold (PLEM); a subsea Pipe Line EndTermination (PLET); and/or a subsea Flow Line End Termination (FLET).

Embodiments of the invention use remotely operated vehicle (ROV) hotstab systems for hydraulic control and fluid sampling. ROV hot stabtools are known in the art, but are generally limited to basic fluidline coupling applications. Conventional ROV hot stabs have at bestlimited sealing capabilities which often result in discharge of fluidsto the surrounding environment. In hydraulic control applications, thismay not be a significant problem; hydraulic fluids are of knowncomposition and the discharge to a subsea environment may not be asignificant environmental issue. Nevertheless, loss or discharge of somehydraulic fluids may generally be undesirable, particularly in low- orzero-discharge production regimes. More significantly, in samplingapplications the discharge of production fluid samples leads topotential for environmental contamination. In sampling applications itis also desirable to have the ability to completely flush an ROV hotstab to avoid contamination between different production fluid samples.Preferred embodiments of the invention therefore use improved hot stabdesigns will be described with reference to FIGS. 8A and 8B (and whichalso form an alternative aspect of the invention).

FIG. 8A is a sectional view of a hot stab and receptacle combination,generally shown at 300. The hot stab receptacle 302 is a standardreceptacle, as is found a range of subsea equipment including existingisolation valve testing and control blocks and sampling valve blocks.The hot stab 304 comprises a hot stab body 306 configured withappropriate shape and dimensions to be received in the standard hot stabreceptacle 304.

The hot stab 304 differs from a conventional hot stab in that itcomprises an internal bore 308 which is axially aligned and extendsthrough the hot stab body 306 from a control end 310 to a leading end312 of the body. First, second and third radial ports 314 a, 314 b, 314c to the internal bore are located in axially separated positions alongthe hot stab body 306, with associated needle valves 315. The hot stab304 is also provided with an internal valve, comprising a directionalcontrol spool 316 which can be moved between different positions in thehot stab body 306 to control various flow combinations. Flow barriers318 a, 318 b are located in axially separated positions on the spool 316to control the axial flow paths through the hot stab.

In the position shown in FIG. 8A, the directional control spool islocated in a closed position, with the spool disposed away from theleading end 312 of the hot stab (to the left as drawn). In thiscondition, fluid is free to flow from port 314 a to port 314 b, via theinternal bore and between the flow barriers 318 of the directionalcontrol spool.

FIG. 8B shows the hot stab 304 in an open position, in which thedirectional control spool 316 has been moved further into the hot stabbody (to the right as drawn) towards the leading end 312. The movementof the directional control spool moves the flow barrier 318 a in thecontrol spool from one side of the port 314 b to the opposing side ofthe opening 314 b. The flow barrier 318 a in this position prevents flowbetween port 314 a and port 314 b, but opens a flow path between port314 b and port 314 c.

In this embodiment, the hot stab is energised by a hydraulic signal fromline 320, although in alternative embodiments an electrical actuationsignal can be provided. Also in this embodiment (and as shown in FIG.8A) the hot stab is provided with a closing spring 322 which biases theposition of the directional control spool 316 to the closed position (tothe left as shown).

The addition of an axial bore 308 and directional control spool 316 to ahot stab converts the hot stab and receptacle combination into adirectional control valve (with two positions in the example describedabove). A hot stab derived directional control valve as described hasmany practical applications, including but not limited to taking fluidsamples from subsea oil and gas flow systems and infrastructure.Application to a fluid sampling system will now be described by way ofexample only with reference to FIG. 9.

FIG. 9 is a schematic view of a sampling circuit, generally shown at400, which utilises an ROV test hot stab 402 and an ROV sampling hotstab 304 to deliver a sampling fluid to a sample collection vessel 404.The sample collection vessel 404 is pre-charged with an inert fluid suchas nitrogen. The sampling hot stab 304 is a valved hot stab as describedwith reference to FIGS. 8A and 8B, and is associated with the samplecollection vessel 404, initially docked into a test valve receptacle ofthe sample collection vessel.

In the preparatory steps, a sampling LARS (not shown) is used to deploythe sample collection vessel 404, which forms a part of a samplingcarousel, to depth. An ROV flies the sample collection vessel 404 to thelocation of the sampling apparatus (not shown), which may for example bethe apparatus of any of FIGS. 3 to 7. The sampling carousel is locatedon a pressure cap locator, and the ROV indexes the carousel to accessthe first sample collection vessel 404.

A sealing hot stab (not shown) is removed from receptacle 302 and parkedin a spare receptacle on the carousel. The sampling hot stab 304 isremoved from the test valve receptacle 406 of the sample collectionvessel 404 and placed in the receptacle 302, as shown in FIG. 9. In theposition shown, the directional valve formed by the hot stab 304 andreceptacle 302 is closed, and provides a flow path between ports 314 aand 314 b. Port 314 b is connected via a needle valve 315 b to thesampling port of the sampling apparatus and port 314 a is connected viaa needle valve 315 a to a pressure test flow line in an upper part ofthe sampling apparatus.

The ROV test hot stab 402 is located into the vacated sample collectionvessel receptacle 406, and the ROV test hot stab 406 is pressurised toenergise the internal spool valve 316 of the sampling hot stab 304 andsimultaneously force down the sample collection vessel decanting piston408. The sample hot stab 304 is opened to create a flow path from theport 314 c (connected to the sample collection vessel) and the opening314 b (connected to the sampling port of the sampling chamber), and thefluid pre-charged in the sample collection vessel 404 is flushed throughthe sampling port, into the sampling chamber, and into the productionbore, simultaneously cleaning all of the interconnection hoses and thesampling hot stab 304.

The test hot stab pressure is held for a period to allow sample chamberto stabilise, and then is slowly reduced to a value just below theflowing well pressure. This action allows the contents of the samplechamber to be pumped, by well pressure, under control into the samplecollection vessel 404. The ROV monitors the sample collection vessel 404until a piston indicator rod is seen rising through the samplecollection vessel cap, and the test hot stab pressure is reduced toambient pressure.

The sampling cavities, including the flow lines to the receptacle 302and the sampling hot stab 304 itself can then be flushed by relocatingthe ROV test hot stab 402 in a test needle valve block (not shown) incommunication with the sampling hot stab port 314 a. With the samplinghot stab 304 closed, and the needle valve 315 b initially closed, needlevalve 315 a is opened to expose the port 314 a to hydraulic pressurefrom ROV test hot stab 402. The needle valve 315 b is briefly opened andclosed to flush fluid through the sampling cavities of the sampling hotstab 304. After pressure testing the needle valves 315, the sampling hotstab 304 is removed and located in the receptacle 406 of the samplecollection vessel. The procedure can be repeated for multiple bottles asdesired or until the bottles are used.

A significant advantage of the use of an internal valve hot stab asdescribed is that in a sampling application, fluid conduit lines can beeasily flushed, and potential environmental contamination associatedwith the leaking of production fluid samples to the subsea environmentcan be mitigated or eliminated. It will be appreciated that a range ofother applications are facilitated by this aspect of the invention. Byaltering the control spool sealed positions, a number of differentcombinations of flow path may be incorporated into the design.

The invention in one of its aspects provides a connection apparatus fora subsea hydraulic circuit and method of use in a sampling application.The apparatus comprises a longitudinal body configured to be removablydocked with a subsea hydraulic circuit receptacle. The body comprises aplurality of radial ports axially displaced along the body, and an axialbore accommodating a spool having at least one fluid barrie. The spooland fluid barrier are actuable to be axially moved in the bore tocontrol axial flow paths along the bore between the plurality of radialports. The apparatus may be configured as a sampling hot stab in anapplication to sampling a production fluid from a subsea hydrocarbonproduction system.

Aspects of the invention facilitate injection and sampling through acombined unit which provides an injection access point and a samplingaccess point. However, the invention in its various aspects also hasapplication to a range of intervention operations, including fluidintroduction for well scale squeeze operations, well kill, hydrateremediation, and/or hydrate/debris blockage removal; fluid removal forwell fluid sampling and/or well fluid redirection; and/or the additionof instrumentation for monitoring pressure, temperature, flow rate,fluid composition, erosion and/or corrosion.

The apparatus and systems of embodiments described herein provideeffective fluid sampling in a compact unit which is convenient,reliable, safe, and relatively low cost to deploy. The samplingapparatus of aspects and embodiments of the invention provide flexibleoperating options, including compatibility with control systems forinjection and/or sampling operations.

Various modifications may be made within the scope of the invention asherein intended, and embodiments of the invention may includecombinations of features other than those expressly described herein.

1. A connection apparatus for a subsea hydraulic circuit, the connectionapparatus comprising: a longitudinal body configured to be removablydocked with a subsea hydraulic circuit receptacle, the longitudinal bodycomprising a plurality of radial ports axially displaced along the body;wherein the body comprises an axial bore accommodating a spool having atleast one fluid barrier; and wherein the spool and fluid barrier areactuable to be axially moved in the bore to control axial flow pathsalong the bore between the plurality of radial ports.
 2. The connectionapparatus according to claim 1, wherein the fluid barrier is an annularfluid barrier arranged to seal an annulus between the spool and thebore.
 3. The connection apparatus according to claim 1, wherein theapparatus comprises at least three radial ports.
 4. The connectionapparatus according to claim 1, wherein the spool and fluid barrier areactuable to be axially moved from a first position in which a flow pathbetween a first port and a second port is open, and a second position inwhich a flow path between the second port and a third port is open. 5.The connection apparatus according to claim 1, wherein in the firstposition, a flow path from the third port to the first or second portsis closed.
 6. The connection apparatus according to claim 1, wherein inthe second position, a flow path from the first port to the second orthird ports is closed.
 7. The connection apparatus according to claim 1,wherein the apparatus is configured as a hot stab apparatus.
 8. A methodof collecting a sample of fluid from a hydrocarbon production system,comprising using the apparatus of claim 1 to deliver a sample of fluidfrom the hydrocarbon production system to a sample collection vessel. 9.The method according to claim 8 comprising flushing the connectionapparatus to remove fluid from the apparatus after the delivery of thesample to the sample collection vessel.
 10. A method of collecting asample of fluid from a hydrocarbon production system, the methodcomprising: providing a sample collection vessel and a sampling hot stabapparatus in fluid communication with the sample collection vessel;locating the sampling hot stab apparatus in a receptacle of thehydrocarbon production system, the receptacle being in fluidcommunication with a production fluid in the hydrocarbon productionsystem; collecting production fluid in the sample collection vessel viathe sampling hot stab apparatus; flushing the sampling hot stabapparatus prior to removal of the sampling hot stab apparatus from thereceptacle.
 11. The method according to claim 10, comprising providing atest hot stab apparatus, and coupling the test hot stab apparatus to thesample collection chamber and/or hydrocarbon production system.
 12. Themethod according to claim 10, comprising decanting a pre-charged fluidfrom the sample collection vessel into the hydrocarbon productionsystem.
 13. The method according to claim 12, comprising controlling thedecanting of the pre-charged fluid from the sample collection vesselusing the test hot stab apparatus.
 14. The method according to claim 12,wherein decanting the pre-charged fluid from the sample collectionvessel comprises flushing the sampling hot stab apparatus.
 15. Themethod according to claim 11, comprising controlling the collection ofproduction fluid into the sample collection vessel using the test hotstab apparatus.
 16. The method according to claim 11, comprisingflushing the sampling hot stab apparatus using a hydraulic fluid sourcecoupled to the test hot stab apparatus.
 17. The method according toclaim 11 comprising controlling the flow of fluid through the samplinghot stab apparatus using the test hot stab apparatus.
 18. The methodaccording to claim 10 wherein the sampling hot stab apparatus is a hotstab apparatus according to claim
 7. 19. The method according to claim18 comprising actuating movement of the spool and fluid barrier of thehot stab apparatus using the test hot stab apparatus.
 20. A system forcollecting a sample of fluid from a hydrocarbon production system, thesystem comprising: a subsea hydraulic circuit comprising a samplecollection vessel, a connection apparatus, and a receptacle for ahydraulic interface apparatus; wherein the connection apparatus isconfigured to be coupled to the production system to connect thehydraulic circuit to the production system; wherein the hydrauliccircuit is configured to enable a production fluid to be delivered tothe sample collection vessel via the connection apparatus; and whereinthe hydraulic circuit is configured to enable flushing of at least theconnection apparatus.
 21. The system according to claim 20 wherein thehydraulic circuit is configured to enable flushing of the connectionapparatus by actuation of the hydraulic interface apparatus.
 22. Thesystem according to claim 21 wherein the hydraulic circuit is configuredto enable flushing of the connection apparatus from a hydraulic fluidsource coupled to the hydraulic interface apparatus.
 23. The systemaccording to claim 21 wherein the hydraulic circuit is configured toenable flushing of the connection apparatus with a pre-charged fluiddecanted from the sample collection chamber.
 24. The system according toclaim 20, wherein the connection apparatus is a connection apparatusaccording to claim
 1. 25. The system according to claim 20, wherein thehydraulic interface apparatus is an ROV test hot stab.
 26. The systemaccording to claim 20, wherein the system comprises a combined fluidinjection and sampling apparatus.
 27. A hot stab apparatus for aremotely operated vehicle, the hot stab apparatus comprising: alongitudinal body configured to be removably docked with a hot stabreceptacle, the longitudinal body comprising a plurality of radial portsaxially displaced along the body; wherein the body comprises an axialbore accommodating a spool having at least one fluid barrier; andwherein the spool and fluid barrier are actuable to be axially moved inthe bore to control axial flow paths along the bore between theplurality of radial ports.
 28. A remotely operated vehicle comprisingthe connection apparatus according to claim
 27. 29. A subsea productionfluid sample collection system comprising the connection apparatus ofclaim 1.